A metal-oxide-semiconductor field-effect transistor (MOSFET) is a transistor used for amplifying or switching electronic signals, and includes a metal oxide gate electrode. N-type field effect transistors (NFETs) and p-type field effect transistors (PFETs) are two types of complementary MOSFETs. An NFET includes n-doped source/drain regions and utilizes electrons as current carriers, whereas a PFET includes p-doped source/drain regions and uses holes as current carriers.
Complementary metal-oxide semiconductor (CMOS) technology is being continuously scaled down with respect to device channel length and contact length. As the channel length reaches tens of nanometers, contact resistance can become comparable with channel resistance, and gradually limit transistor drive current.
Due to its superior electrical properties and intrinsic ultra-thin body, carbon nanotube (CNT) is widely considered as one of the most promising candidates to replace silicon for sub-5 nm technology nodes. CNT-based CMOS technology requires a scalable transistor channel and scalable and robust source/drain contacts for both PFETs and NFETs. For this purpose, end-bonded source/drain metal contacts to CNTs, featuring a length-independent contact resistance, represent a preferred contact scheme over side contacts for scaled technology nodes.